What you're listening to there is audio from Iranian state television last night. They were broadcasting live the launch of ground-to-ground missiles into eastern Syria targeting ISIS. This is the first such missile strike from Iran since the Syria conflict began six years ago. Iran says this was in retaliation for the recent ISIS terror attacks in Tehran. NPR's Peter Kenyon has been following all of this from his post in Istanbul. Good morning, Peter.

PETER KENYON, BYLINE: Hi, David.

GREENE: So what exactly did Iran do here?

KENYON: Well, the Revolutionary Guard Corps - they say it was six mid-range, ground-to-ground missiles launched from western Iran across Iraqi airspace and into Deir ez-Zor in eastern Syria. Now, the guards say the targets included an ISIS command center, a facility for making vehicle bombs. Those claims haven't been confirmed yet, we should note. A news agency close to the guards, the Tasnim News Agency, says these strikes were coordinated with Syrian military. And, as you say, this was the first time they've hit here since 2011, when it began.

GREENE: Yeah, this is a big deal, right? I mean, so does it change the Syrian conflict in some way?

KENYON: Well, that is a question a lot of people will be having. There has been some boasting on Iranian social media, hardliners saying how - you think this is bad; wait until you see what's next - that sort of thing. But all the official statements, so far, are very explicit. This was in retaliation for the June 7 attacks in Tehran. Those left 18 people dead, more than 50 wounded. They were claimed by ISIS.

And, you know, they deeply shocked Iranians, who had believed their government when it told them that Iran was safe from terrorism. It wouldn't happen there. So I would say this is not a general escalation based on what we know, so far, by Iran. If these missile strikes were to continue, that would definitely complicate things. It's already a very crowded battle space there.

GREENE: Yeah, crowded and complicated. And I don't have to tell you that, since you're the one who has the hard job of explaining it to us all the time. But can I ask you this? I mean, you have Iran targeting ISIS. The United States targets ISIS. But when Iran fires missiles, does that raise concerns in the U.S. or in - among its allies about Iran's missile capabilities?

KENYON: Well, I think it will. I mean, critics have long warned, especially about Iran's ballistic missile capacity. They want strong actions to constrain it. There have been sanctions. It was one of the complaints against the nuclear deal in 2015, that it did not address this missile program. Iran, of course, says, look, this is all defensive, nothing to do with the nukes. There is a constant watch, I should say, for Iran testing missiles that could be capable of carrying a nuclear warhead. And the big concern, of course, with Iranian missiles would be longer-range missiles - ones capable, say, of reaching Israel.

GREENE: And I guess we should note that this is extraordinary, not just because Iran did this, but these strikes came on the same day that the U.S.-led coalition shot down a Syrian fighter jet for the first time. How does that fit in here?

KENYON: Well, not related, as far as we know. But it is another first - a busy day in Syria, Sunday. It was an American F-18 that shot down a Syrian SU-22 warplane after the Syrian jet dropped bombs close to U.S.-backed rebel forces. This all happened southwest of Raqqa, where the coalition against ISIS is battling to get them out of there.

Syrian ally Russia is already voicing its unhappiness, saying you shouldn't be using force against the Syrian military. And the Americans say, this was within the rules. It was protecting forces on the ground that are there to fight ISIS, not the regime. But obviously, another sign of just how complicated this is.